The present invention relates to an optical connector and a shield case which are useful in the field of optical communication for OA, FA, vehicle apparatuses, and the like.
A related optical connector which accommodates and holds an optical element D such as a light emitting element or a light receiving element is shown in FIG. 5.
In the optical connector, in order to improve the noise resistance of the optical element D against external noises and suppress radiative noises from the optical element D, the optical element D is accommodated in a metal shield case 101 and then mounted into a connector housing 105 which is made of a resin.
A lead terminal 102 downward elongates from the shield case 101. When the optical connector is mounted and fixed to a circuit board P, the lead terminal 102 is passed through a through hole Ps formed in the circuit board P, and then soldered to a grounding wiring pattern formed on the lower face of the circuit board, whereby the shield case 101 is grounded.
A pair of fixing pieces 106 each having a screw hole 106h are formed on rear portions of both the sides of the connector housing 105, respectively, and screw through holes Ph are formed in the circuit board P. In a state where the connector housing 105 is placed on the circuit board P, screws S are passed from the lower side of the circuit board P through the screw through holes Ph, whereby the optical connector is mounted and fixed to the circuit board P.
In the optical connector, in order to improve the shielding performance of the shield case 101, it is required to lower the grounding resistance of the shield case 101.
As a configuration which can satisfy the requirement, a configuration may be employed in which a plurality of lead terminals 102 are disposed on the shield case 101 and the plurality of lead terminals 102 are soldered to grounding wiring patterns on the circuit board P.
In this case, the grounding wiring patterns to which the lead terminals 102 are to be soldered must be formed on the rear face of the circuit board P. This increases the restriction imposed on the circuit design.
When the optical connector is to be mounted and fixed to the circuit board P, the plural lead terminals 102 must be passed through through holes Ps formed in the circuit board P, respectively, thereby causing a problem in that the workability of mounting and fixing the optical connector is low.
Therefore, it may be contemplated to employ an optical connector which is configured in the following manner. A pair of plate-like grounding pieces are formed on both the side edges of the shield case 101 so as to overlap with the lower sides of the fixing pieces 106, respectively. When the fixing pieces 106 are to be screwed and fixed to the circuit board P, the grounding pieces are interposed between the fixing pieces 106 and the circuit board P to be in surface contact with the grounding wiring patterns formed on the circuit board P, respectively.
This optical connector is configured so that the grounding pieces are in surface contact with the grounding wiring patterns Therefore, the grounding resistance of the shield case 101 can be lowered without forming a plurality of lead terminals 102 on the shield case 101.
In the case where such grounding pieces are curved or bent to have problems in flatness and distortion, or the pair of grounding pieces are relatively shifted or twisted, however, the electrical and thermal connecting states between the shield case 101 and the grounding wiring patterns are impaired and the attaching state becomes unstable. In such a case, when the screws are compulsorily fastened by applying a strong force in order to cause the grounding pieces to be firmly in surface contact with the grounding wiring patterns, an excessive force is applied to the shield case 101, the optical element D, and the connector housing 105, thereby producing problems that the optical axis is deviated, and the such components are damaged. Therefore, such compulsive screw fastening cannot be conducted.
It is an object of the invention to provide an optical connector and a shield case in which electrical and thermal connecting states between a shield case and a grounding wiring pattern of a circuit board can be improved and stable attachment can be conducted without disposing a plurality of leads.
In order to solve the problem, an optical connector of a first aspect of the invention is an optical connector in which a plate-like grounding piece is formed on a shield case that is capable to accommodate an optical element, a plate-like fixing piece is formed so as to overlap with the grounding piece, on a connector housing that is capable to accommodate the shield case, and, in a state where the optical connector is mounted and fixed to a circuit board, the grounding piece is pressed against the circuit board by the fixing piece, wherein at least one spring piece is formed by cutting, raising, and bending a part of the grounding piece, the spring piece being elastically deformable to be flattened in a raising region between the circuit board and the fixing piece.
In a second aspect of the invention, the spring piece has a shape which is obtained by cutting and raising the part of the grounding piece in a strip-like shape, and bending an intermediate portion in a longitudinal direction of the raised part into a substantially V-like shape.
In a third aspect of the invention, a plated layer is formed on a portion of the spring piece, the portion being to be in contact with a wiring pattern of the circuit board.
A shield case of a fifth aspect of the invention is a shield case which is capable to accommodate an optical element, wherein a plate-like grounding piece which is to be pressed against a circuit board is formed, and at least one spring-like projection is formed on the grounding piece by cutting, raising, and bending a part of the grounding piece.